Method for painting inner surface of pipe

ABSTRACT

A method and apparatus for interior painting of pipe, particularly of small diameter, is characterized by filling of a pipe with both ends open with paint, hanging the pipe vertical and passing a ball of a diameter smaller than the inside diameter of the pipe from the upper end of the pipe to fall down by its gravity through the pipe and strip off excessive paint so as to form a film of uniform thickness of paint of the inner surface of the pipe.

States Patent asano et a1.

[15] 3,657,000 51 Apr. 18,197

METHOD FOR PAINTING INNER SURFACE OF PIPE Inventors: Kimiaki Kasano,Amagasaki-shi, l-lyogoken; Ichiro Kaya, Sakai-shi, Osaka-fu,

both of Japan Assignee: Kansai Paint Company Limited, Hyogoken, JapanFiled: June 23, 1969 Appl. No.: 835,705

Foreign Application Priority Data July 2, 1968 Japan ..43/46399 U.S. Cl...117/97, 117/132 B, 117/132 BE, 117/132 C, 117/161 KP, 117/161ZB,118/105, 118/408, 118/DIG. 10

Int. Cl. ..B44d l/09, 844d 1/02 Field of Search ..117/95, 97, 64, 161KP, 1612B; 118/408, 105, DIG. 10; 166/163 [5 6] References Cited UNITEDSTATES PATENTS 2,100,587 11/1937 Chalker ..118/105 2,318,060 5/1943Cortese ..1 17/97 X Primary Examiner-Alfred L. Leavitt AssistantExaminer-Edward Whitby At!0rneyLars0n, Taylor, and Hinds [5 7] ABSTRACTA method and apparatus for interior painting of pipe, particularly ofsmall diameter, is characterized by filling of a pipe with both endsopen with paint, hanging the pipe vertical and passing a ball of adiameter smaller than the inside diameter of the pipe from the upper endof the pipe to fall down by its gravity through the pipe and strip offexcessive paint so as to form a film of uniform thickness of paint ofthe inner surface of the pipe.

3 Claims, 4 Drawing Figures METHOD FOR PAINTING INNER SURFACE OF PIPEThis inventionrelates to a method for painting the inner surface of apipe and is aimed at providing pipe particularly of small diameter withinner surface evenly painted.

In the conventional methods uniform coating of the inner surface of apipe extremely large inside diameter could be performed by means ofspraying, but with long pipe of smaller inside diameter, such as lessthan 53 mm inside diameter, uniform coat of the inner surface could notbe obtained. And, for example, when a pipe of smaller diameter is firstfilled with paint, and then the pipe is hung vertical to let paint inexcess flow down, there inevitably results difference in the thicknessof coat between at lower and upper ends, failing to provide uniformthickness of the coat, and is accompaniedby sagging and furthermore ittakes longer time in coating work. No such sprayer is known in the art,being capable of painting the inner surface of a pipe of less than 53 mminside diameter. Also high viscosity paint can not be used in spraypainting for this purpose.

The object of the invention is to provide a method for forming uniformcoat of paint by a simple operation by using a relatively high viscositypaint in painting the inner surface of a pipe, particularly of smalldiameter. According to the invention, in forming a film of uniformthickness on the inner surface of a pipe with open ends, the pipe isfirst filled with paint, and then hung vertical, and preferably, afterthe paint has partly flowed down, then a ball having diameter slightlysmaller than the inside diameter of the tubular body is inserted throughthe upper end of the pipe to fall down through the hollow, wherebyuniform film is formed on the inner surface of the pipe. Thus, accordingto the invention uniform film of paint as desired is formed, by firstfilling the hollow portion of a pipe with both ends open with paint,hanging the pipe substantially vertical, preferably, after letting thepaint within fall down to some extent, and then passing aball of adiameter allowing a clearance necessary for producing required thicknessof film, from upper end of the pipe to fall down by its gravity, so asto strip off excessive paint.

The invention will be hereinafter explained according to the attached,drawings, in which.

FIG. 1 is a side elevation with a partial longitudinal section of apreferred embodiment of the invention.

FIG. 2 is enlarged longitudinal section of part of FIG. 1.

FIG. 3 is a sectional view along AA line of FIG. 2. and

FIG. 4 is an enlarged sectional view along B-B line of FIG. 1.

In FIG. I, pipe 1 is suspended from tact-conveyor 3 by hanger 2, saidtact conveyor moving intermittently at regular intervals in thedirection of arrow head. When pipe I hung on tact conveyor 3 reachespaint inlet 5 by movement of tact conveyor 3, tact conveyor stops, paintinlet 5 moves upward actuated by arm operator 6 held by stay 21, to fitthe lower opening of pipe 1. Then coating composition in tank 8is'pumped into pipe 1 by pump 7 through hose l9 and hollow arm 4. Whenpipe 1 is filled to the upper extremity, paint inlet 5 and hollow arm 4are lowered by arm operator 6, and tact conveyor again moves in thedirection of arrow head.

On the other hand, the ball is supplied to pipe 1 in the followingmanner during operation. Number of balls are kept in box 20 provided onthe upper part of tact conveyor 3, and when pipe filled with paint atthe upper end or its vicinity as above reaches below ball outlet 23 ofbox 20, shutter 22 at the outlet 23 of box 20 opens and a ball islowered to the upper opening of pipe 1 below the outlet 23. When shutter22 is opened shutter 25 provided in ball feed pipe 24in a distance fromshutter 22 of slightly larger than the diameter of ball 13 is shut tolet only one ball drop from ball exit 23. When ball 13 has droppedshutter 22 is shut whereby another ball is delivered into pipe 24. Allthe above supply of paint into pipe and the supply of ball 13 arecarried out automatically by means of a regulator.

The above operation takes place in a given length of time, and conveyor3 is driven again by means of time switch. The supply of the balls mayalso be done manually. Ball 13 in pipe 1 falls by gravity within thepipe while conveyor 3 is moving, forcing down paint 16 to producerequired thickness of film l8. Hanger 2 provided on conveyor 3 isequipped with at least a pair of catches 27 having teeth 26 at the end,facing diagonally and movable up and down, and between these opposingcatches 27 pipe 1 is inserted and by slightly lowering pipe 1 teeth 26of catches 27 engage with outside surface of pipe I to be suspended.Balls falling through pipe 1 are collected in ball receptacle l5, andare washed for reuse in a separate tank with an organic solvent whichdissolves the paint. Excessive paint 16 which is stripped off from pipe1 is delivered to paint tank 8 for recirculation. Pipes 1 on which filmof paint is formed further move successively and are baked as requiredby baking oven 17 to obtain final products. In this way of painting, thecoated film is sufficiently thin according to the viscosity of paintused after the ball is passed through and no sagging is liable to occur.The manner of the ball passing through pipe 1 is shown in FIG. 2 and 3.in-enlarged drawings. In FIG. 2 and 3, the paint filling the pipe 1 isstripped off by ball 13 to result in desired thickness of coat. In theinvention, the method of filling pipe 1 with paint is not limited tofilling from the lower end, and it can be done, for example, by pluggingthe bottom end of pipe 1 and charging it from upper end and removing theplug for further operation.

When the ball is inserted from the upper end of pipe 1 it is inevitablethat the ball is somewhat shaken in the direction of the diameter of theball for a length of about 10-20 mm from the upper end, but after thatthe ball will fall straight through the center of pipe 1. Accordingly,either by cutting off such length of 10-20 mm from the end or bytemporarily joining a sperate pipe of same inside diameter to the upperend of pipe 1 for coating and removing it after coating, uniformthickness of the coat can be obtained throughout.

The prefered embodiment of the present invention is advantageous in thatafter filling pipe 1 with paint, the paint is allowed to partly falldown (see drawings) to let the ball fall through-the center of piperapidly, whereby the thickness of film within is unified. I

The paints to be used in the invention may vary, but generally tar-epoxyresin-based paints of viscosity of about 60-130 KU (Krebs Unit),polyvinyl chloride sol-based paints of about -110 KU, epoxy resin-basedpaints of about 60-130 KU and polyurethane resin-based paints of about60-90 KU, etc. are used. These paints are selected by considering theinside diameter of pipe to be painted, thickness of film to be formed,specific gravity of balls used, etc. As the balls to be used aredesirable those of a material having specific gravity of about l.0-8.0.Steel balls (specific gravity of about 7.8), Porcelain balls (generallyspecific gravity of about 3.5), plastics balls (generally specificgravity of about 1.0-2.0), stainless steel balls (generally specificgravity of about 7.8), glass balls (generally specific gravity about of2.2-6.3), etc. can be effectively used. The diameter of these balls isselected in consideration of inside diameter of pipe and clearance fromsaid inside diameter of pipe, necessary to produce film of paint to thedesired thickness. The clearance generally is about 1.3-2 times thedesired thickness of film depending on the concentration of paint, forexample, the clearance of about -220 g is desirable to obtain a film 110 ,u. thick. The specific gravity of the balls can be selected freelyaccording to the viscosity of paint and the diameter of pipe. The methodof the invention can be most advantageously applied to the painting ofsteel pipe of 12.7 mm 52.9 mm inside diameter. The pipe, ball and paintin various combinations according to the method of the invention areexemplified in Table 1 below.

A SGP (12.7) Steel 70-80 60-80 A SGP l6.l) Steel 7.0-8.0 60-110 A SGP (2l .6) Steel 70-80 60-110 A SGP (27.6) Steel 7.0-8.0 60-130 32A SOP(35.7) Steel 7.0-8.0 60-130 40A SGP (41.6) Steel 70-80 90-130 Porcelain3.0-4.0 60-90 50A SGP (52.9) Porcelain 3.0-4.0 90-130 Plastics l.0-2.060-90 In the method of the invention it is also possible to introducerelatively pressurized air into pipe after inserting the ball from theupper opening of pipe to facilitate the fall of the ball through pipe.

The method of the invention can be said to have an extremely highindustrial value in that the interior surface of a pipe of smallerdiameter is painted to uniform and desired thickness by a simpleoperation.

Concrete explanation of the method of the invention is done by Examplesto follow.

EXAMPLE 1 By the equipment as shown in FIG. 1 interior coating wascarried out under the following conditions:

between pipes Speed oftact conveyor Stop 35 sec. and advance 5 sec.

Drying conditions No sagging was observed in the film immediately aftercoating and after minutes, and uniform film of 210:15 u was obtained.The upper end of the pipe was cut off by 10 mm.

EXAMPLE 2 By the equipment of FIG. 1 was conducted interior paintingunder the following conditions.

TABLE 3 inside l2.7 mm 52.9 mm diameter (10A SGP) (50A SGP) Pipe Length5.5 m 5.5 m Material Steel Steel Diameter 12.2 mm 52.0 mm Ball Weight7.4 g 260 3 Material Steel Porcelain Viscosity 60 KU 1 l0 KU Paint TypeEpoxy-resin Tar-epoxy based enamel resin-based enamel Clearance 0.25 mnt0.45 mm Falling ve- 43-50 sec/ l5-l8 sec/ Operlocity of ball 5.5 m 5.5 mation con- Distance be- 50 mm 50 mm ditions tween pipes Speed of tactStop 60 sec Stop 20 sec conveyor Advance 5 sec Advance 5 sec Dryingconditions CXIS min. 20 C:5 24 hr.

By coating under the above conditions A and B, the thickness of obtainedfilm was i 10120 n for A and 300135 a for B, and the thicknesses weresubstantially uniform throughout, exhibiting no notable differencesbetween upper and lower parts, and even after 30 minutes verticalsuspension of the pipes no sagging was observed.

What we claim are:

1. A method for painting the interior of a pipe comprising filling apipe having both ends open with paint while said pipe is hangingvertically and permitting a ball of a diameter slightly smaller than theinside diameter of the pipe from the upper end of the pipe to fall downthrough the hollow portion of the pipe under gravitational forces onlyso as to form a film of uniform thickness of paint on the inner surfaceof the pipe.

2. A method according to claim 1 wherein said pipe comprises ferrousmetal.

3. A method according to claim 2 wherein said pipe comprises steel pipehaving an inside diameter of 12.7 to 52.9 mm.

2. A method according to claim 1 wherein said pipe comprises ferrousmetal.
 3. A method according to claim 2 wherein said pipe comprisessteel pipe having an inside diameter of 12.7 to 52.9 mm.